Placement of coiled catheters into the paravertebral space*

Empirical guide to a safe thoracic paravertebral block based on dimensions of paravertebral space when ultrasound visualization is challenging

Although ultrasound (US) guidance is the mainstay technique for performing thoracic paravertebral blocks, situations arise when US imaging is limited due to subcutaneous emphysema or extremely deep structures. A detailed understanding of the anatomical structures of the paravertebral space can be strategic to safely and accurately perform a landmark-based or US-assisted approach. As such, we aimed to provide an anatomic roadmap to assist physicians. We examined 50 chest CT scans, measuring the distances of the bony structures and soft-tissue surrounding the thoracic paravertebral block at the 2nd/3rd (upper), 5th/6th (middle), and 9th/10th (lower) thoracic vertebral levels. This review of radiology records controlled for individual differences in body mass index, gender, and thoracic level. Midline to the lateral aspect of the transverse process (TP), the anterior-to-posterior distance of TP to pleura, and rib thickness range widely based on gender and thoracic level. The mean thickness of the TP is 0.9±0.1 cm in women and 1.1±0.2 cm in men. The best target for initial needle insertion from the midline (mean length of TP minus 2 SDs) distance would be 2.5 cm (upper thoracic)/2.2 cm (middle thoracic)/1.8 cm (lower thoracic) for females and 2.7 cm (upper)/2.5 cm (middle)/2.0 cm (lower thoracic) for males, with consideration that the lower thoracic region allows for a lower margin of error in the lateral dimension because of shorter TP. There are different dimensions for the key bony landmarks of a thoracic paravertebral block between males and females, which have not been previously described. These differences warrant adjustment of landmark-based or US-assisted approach to thoracic paravertebral space block for male and female patients.

[Ultrasound-guided low-volume continuous cervical sympathetic nerve block for treatment of an electrical storm]

In addition to the treatment for complex regional pain syndrome (CRPS), the stellate ganglion block is a treatment option for refractory intermittent ventricular tachycardia (VT). Despite the use of imaging techniques, such as fluoroscopy and ultrasound, numerous side effects and complications have been reported. These are a result of the complex anatomical site and the volume of injected local anesthetics. This article reports on the catheter placement for continuous block of the cervical sympathetic trunk with high-resolution ultrasound imaging (HRUI) in a patient with intermittent VT. The tip of the cannula was placed on the anterior aspect of the longus colli muscle and 20 mg prilocaine 1% (2 ml) was injected. The VT stopped and a continuous infusion of 1 ml/h ropivacaine 0,2 % was started. Nevertheless, during the next hour the patient developed hoarseness and dysphagia, so that a block of the recurrent laryngeal nerve and the deep ansa cervicalis (C1-C3) was carried out. The infusion was paused and restarted later with 0.5 ml/h. The spread of the local anesthetic was controlled by ultrasound. Over the next 4 days the patient showed no VT or detectable side effects. After implantation of a defibrillator 1 day later the patient could then be discharged home on the following day. This case shows that the HRUI can be advantageously used in the catheter placement and also when adjusting the flow rate. In this way the risk of complications and side effects related to the puncture and local anesthetic volume can be reduced.

Impact of self-coiling catheters for continuous popliteal sciatic block on postoperative pain level and dislocation rate: a randomized controlled trial

Background

Dislocation of catheters within the tissue is a challenge in continuous regional anesthesia. A novel self-coiling catheter design is available and has demonstrated a lower dislocation rate in a cadaver model. The dislocation rate and effect on postoperative pain of these catheters in vivo has yet to be determined and were the subjects of this investigation.

Methods

After ethics committee approval 140 patients undergoing elective distal lower limb surgery were enrolled in this prospective randomized controlled trial. Preoperatively, patients were randomly assigned and received either the conventional (n = 70) or self-coiling catheter (n = 70) for ultrasound-guided popliteal sciatic nerve block in short axis view and by the in-plane approach from lateral to medial. The primary outcome was pain intensity after surgery and on the following three postoperative days. Secondary outcomes investigated were dislocation rate in situ determined by sonography, catheter movement visible from outside, opioid consumption as well as leakage at the puncture site.

Results

All catheters were successfully inserted. The study population of self-coiling catheters had significantly lower mean numeric rating scale values than the reference cohort on the first (p = 0.01) and second postoperative days (p < 0.01). Sonographic evaluation demonstrated, 42 standard catheters (60%) and 10 self-coiling catheters (14.3%) were dislocated in situ within the first three postoperative days. The externally visible movement of the catheters at insertion site did not differ significantly between groups through the third postoperative day. The opioid consumption was significantly lower in the self-coiling catheter group on the day of surgery and on the second and third postoperative days (p = 0.04, p = 0.03 and p = 0.04, respectively).

Conclusion

The self-coiling catheter offers a better postoperative pain control and a lower dislocation rate within the tissue when blocking the popliteal sciatic nerve compared to a conventional catheter. Further trials in large patient cohorts are warranted to investigate the potential beneficial effects of self-coiling catheters for other localisations and other application techniques.

Trial registration

The trial was registered at German Clinical Trials Register (DRKS) on 08/04/2020 (DRKS00020938, retrospectively registered).

Thoracic-paravertebral blocks: comparative anatomical study with different injection techniques and volumes

Background and objectives

We hypothesized that different injection techniques and volumes in thoracic-paravertebral blocks (TPVB) lead to different patterns of dye spread. In particular, we investigated whether an alternating injection technique leads to complete staining of all adjacent intercostal nerves.

Methods

This comparative anatomical investigation was performed using 10 or 20 mL of dye (Alcian Blue) in 10 unfixed donor cadavers (54 injections) that were designated for education or research purposes.

Results

In landmark-guided TPVB, the thoracic-paravertebral space (TPVS) was either not stained at all (spread of dye in the paraspinal muscles, n=3) or the dye was predominantly found in the epidural space (n=3). In ultrasound-guided TPVB, the TPVS was correctly identified in all cases (n=48). The sympathetic trunk was stained in 84.6% of injections (multi-injection technique: 100%), independent of injection technique and volume. The epidural space was stained more frequently (p≤0.001) if both the puncture site (sagittal transducer position) and guidance of the needle were more medial (77.8%). Finally, a higher injection volume (20 vs 10 mL) resulted in a higher number of stained intercostal nerves (p=0.04).

Conclusion

For ultrasound-guided techniques, a higher injection volume resulted in a larger number of stained intercostal nerves. Staining of the sympathetic trunk was independent of the injection technique. Epidural spread was observed significantly less frequently if the injection was lateral (transducer transversal) or with a strictly cranial injection direction (transducer sagittal). Landmark-guided injections reliably achieved the TPVS (and the epidural space) only after a needle advance of 2.5 cm after initial contact with the transverse process.

Safety, complications and clinical outcome after ultrasound-guided paravertebral catheter insertion for rib fracture analgesia: a single-centre retrospective observational study

Rib fractures are associated with significant morbidity and mortality. Ultrasound-guided thoracic paravertebral catheter insertion has been described for the management of pain secondary to rib fractures. We conducted a retrospective observational study of all patients with rib fractures who had a paravertebral catheter inserted for analgesia provision over a 4-year period. Data from the Trauma Audit and Research Network were used to compare patients with rib fractures who were managed with paravertebral catheters to those managed with systemic analgesia. A total of 314 consecutive paravertebral catheters were inserted in 290 patients. Five (1.9%) catheters were removed due to ineffective analgesia. Other minor complications occurred in three cases (0.96%). The proportion of rib fracture patients managed with paravertebral catheters increased from 31/200 (15.5%) in the first year of study to 81/168 (48.2%) in the fourth; over this time-period the observed:predicted mortality ratio fell from 1.04 to 0.66. Proportional hazard regression with and without propensity score matching demonstrated a reduction in mortality associated with paravertebral catheter use, but this became statistically non-significant when time-dependent analysis was used. Paravertebral catheters are a safe and effective technique for rib fracture analgesia; however, our data were insufficient to demonstrate any improvement in mortality.

Continuous right thoracic paravertebral block following bolus initiation reduced postoperative pain after right-lobe hepatectomy: a randomized, double-blind, placebo-controlled trial

Background and Objectives

We hypothesized that continuous right thoracic paravertebral block, following bolus initiation, decreases opioid consumption after right-lobe hepatectomy in patients receiving patient-controlled intravenous analgesia with sufentanil.

Methods

Patients undergoing right-lobe hepatectomy with a right thoracic paravertebral catheter placed at T7 30 minutes before surgery were randomly assigned to receive through this catheter either a 10-mL bolus of 0.2% ropivacaine before emergence, followed by a continuous infusion of 6 mL/h for 24 hours (PVB group), or saline at the same scheme of administration (control group). All patients were started on patient-controlled intravenous analgesia with sufentanil in the postanesthesia care unit. The primary outcome measure was total sufentanil consumption during the first 24 postoperative hours. P = 0.05 was considered as significant. For the multiple comparisons of data at 5 different time points, the P value for the 0.05 level of significance was adjusted to 0.01.

Results

Sixty-six patients were assessed for eligibility, and a PVB catheter was successfully placed for 48 patients. Data were analyzed on 22 patients in group PVB and 22 patients in the control group. The cumulative sufentanil consumption in the PVB group (54.3 ± 12.1 μg) at 24 postoperative hours was more than 20% less than that of the control group (68.1 ± 9.9 μg) (P < 0.001). There was also a significant difference in pain scores (numerical rating scale) between groups, where the PVB group had lower scores than did the control group at rest and with coughing for the first 24 hours (P < 0.001).

Conclusions

Continuous right thoracic paravertebral block, following bolus initiation, has an opioid-sparing effect on sufentanil patient-controlled intravenous analgesia for right-lobe hepatectomy patients and reduces numerical rating scale pain scores at rest and with coughing in the first 24 postoperative hours.

Use of a perineural coiled catheter at the sciatic nerve in dogs after tibial plateau levelling osteotomy - preliminary observations

The analgesic effects of peripheral nerve blocks can be prolonged with the placement of perineural catheters allowing repeated injections of local anaesthetics in humans. The objectives of this study were to evaluate the clinical suitability of a perineural coiled catheter (PCC) at the sciatic nerve and to evaluate pain during the early post-operative period in dogs after tibial plateau levelling osteotomy. Pre-operatively, a combined block of the sciatic and the femoral nerves was performed under sonographic guidance (ropivacaine 0.5%; 0.3 mL kg^-1 per nerve). Thereafter, a PCC was placed near the sciatic nerve. Carprofen (4 mg kg^-1 intravenously) was administered at the end of anaesthesia. After surgery, all dogs were randomly assigned to receive four injections of ropivacaine (group R; 0.25%, 0.3 mL kg^-1) or NaCl 0.9% (group C; 0.3 mL kg^-1) every 6 h through the PCC. Pain was assessed by use of a visual analogue scale (VAS) and a multi-dimensional pain score (4Avet) before surgery (T-1), for 390 min (T0, T30, T60, T120, T180, T240, T300, T360 and T390) as well as 1 day after surgery (Day 1). Methadone (0.1 mg kg^-1) was administered each time the VAS was ≥40 mm or the 4Avet was ≥5. At T390 dogs received buprenorphine (0.02 mg kg^-1). Data were compared using Mann-Whitney rank sum tests and repeated measures analysis of variance. Regardless of group allocation, 55% of dogs required methadone. VAS was significantly lower at T390 (P = 0.003), and at Day 1 (P = 0.002) and so was 4Avet at Day 1 (P = 0.012) in group R than in group C. Bleeding occurred in one dog at PCC placement and PCC dislodged six times of 47 PCCs placed. Minor complications occurred with PCC but allowed four repeated administrations of ropivacaine or saline over 24 h in 91.5% of the cases.

The location of paravertebral catheters placed using the landmark technique

The aim of this prospective clinical study was to evaluate the location of paravertebral catheters that were placed using the classical landmark puncture technique and to correlate the distribution of contrast dye injected through the catheters with the extent of somatic block. Paravertebral catheter placement was attempted in 31 patients after video-assisted thoracic surgery. In one patient, an ultrasound-guided approach was chosen after failed catheter placement using the landmark method. A fluoroscopic examination in two planes using contrast dye was followed by injection of local anaesthetic and subsequent clinical testing of the extent of the anaesthetised area. In nine patients (29%), spread of contrast dye was not seen within the paravertebral space as intended. Misplaced catheters were in the epidural space (three patients), in the erector spinae musculature (five patients), and in the pleural space (one patient). There was also a discrepancy between the radiological findings and the observed distribution of loss of sensation. We have demonstrated an unacceptably high misplacement rate of paravertebral catheters using the landmark method. Additional research is required to compare the efficacy and safety of continuous paravertebral block using ultrasound-guided techniques or surgical inserted catheters.